The present invention is related to systems and methods for transferring information to and from a storage medium, and more particularly to systems and methods for positioning a sensor in relation to a storage medium.
Various storage media are accessed through use of a read/write head assembly that is positioned in relation to the given storage medium. The read/write head assembly is supported by a head actuator, and is operable to read or sense information from the storage medium and to write information to the storage medium. The distance between the read/write head assembly and the storage medium is typically referred to as the fly height. Control of the fly height is critical to proper operation of a storage system in which the storage medium is deployed. In particular, increasing the distance between the read/write head assembly and the storage medium typically results in an increase in inter symbol interference. Where inter symbol interference becomes unacceptably high, it may become impossible to credibly read the information originally written to the storage medium. In contrast, a fly height that is too small can result in excess wear on the read/write head assembly and/or a premature crash of the storage device.
In a typical storage device, fly height is set to operate in a predetermined range. During operation, the fly height is periodically measured to assure that it continues to operate in the predetermined region. A variety of approaches for measuring fly height have been developed including optical interference, spectrum analysis of a read signal wave form, and measuring a pulse width value of the read signal. Such approaches in general provide a reasonable estimate of fly height, however, they are susceptible to various errors. In some cases, fly height has been measured by utilizing harmonic measurements based upon periodic data patterns written to the user data regions of a storage medium. Such approaches are problematic as they reduce the amount of storage that may be maintained on a given storage medium. In other cases, fly height has been measured during operation using servo data that occurs periodically on a given storage medium. While such an approach addresses some of the previously mentioned limitations, updates can be very slow and at times accuracy can suffer.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for positioning a sensor in relation to a storage medium.